April 5 (Reuters) - Manchester United ( MANU ) manager Erik ten Hag has warned the club's fans to avoid tragedy-related abuse when they host Premier League leaders Liverpool at Old Trafford on Sunday.

The two sides met last month in a thrilling FA Cup tie where United came out on top in extra-time in a 4-3 win and Ten Hag said he wanted the fans to focus on replicating that same atmosphere again on Sunday.

"The atmosphere our fans generated was incredible that afternoon and if we can produce the same noise levels around Old Trafford, then we have already seen what a positive force it can be and the impact that it has on the players," Ten Hag said.

"As such, it is part of my duty to remind every supporter ... that it must be enjoyed in the proper way and not used as an excuse for abusing rival fans about Hillsborough, Heysel or any other historic tragedies."

Last month, United and Liverpool jointly launched an education programme through their foundations to tackle tragedy-related abuse.

The clubs have repeatedly condemned fans chanting in reference to the Hillsborough tragedy, the Heysel Stadium disaster and the Munich air disaster to mock opposition supporters, a practice liable to criminal prosecution.

"This is one of the truly great rivalries in world sport, for so many of the right reasons and it is our responsibility to keep it that way," Ten Hag added.

"Whether the clubs meet at Old Trafford or Anfield, all supporters must focus entirely on backing their team and both (Liverpool manager) Juergen (Klopp) and I trust that we can count on that happening."

Klopp urged fans to "show a bit of class" when things do not go their way in a game.

"In general it's just helpful that we educate our kids in specific things - respect, understanding, all these kind of things," he said.

"So don't sing this or sing that, just show class. Have a fight on the pitch, let's play football. If you want be happy if we lose... that's all fine."

United are sixth in the standings after losing 4-3 at Chelsea in a thriller on Thursday, when Ten Hag's side conceded twice in added time. Liverpool are two points clear at the top after beating Sheffield United 3-1.